| Author |
Message |
    
Agno3
Tinkerer
Username: Agno3
Post Number: 8
Registered: 07-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, November 27, 2009 - 08:31 am: | 
|
This lens does not appear to come aprt the same as the 1.8's do. I need to remove the aperture mechanism for cleaning but cnnot determine how to remove the inner tube into which the front element bridge screws. There appears to be a setscrew holding this and I can't see how to free the helicoid.
I also need to remove the ring holding the A/M switch as grease has migrated there and gummed up the diaphragm return.
Pointers welcome. |
Agno3
Tinkerer
Username: Agno3
Post Number: 9
Registered: 07-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, November 27, 2009 - 11:17 am: |
|
Actually, I realized I have not disassembled a Mamiya/Sekor 1.8 lens. I am looking for assistance with a 55mm f/1.4 lens disassembly. |
Agno3
Tinkerer
Username: Agno3
Post Number: 10
Registered: 07-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, December 01, 2009 - 11:09 am: |
|
Surely someone here knows the secret to this disassembly. |
Mikel
Tinkerer
Username: Mikel
Post Number: 180
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, December 01, 2009 - 01:22 pm: |
|
Is it:
M42 screw mount
Later Auto XTL bayonet mount
Later ze series bayonet mount
Even later NC1000 bayonet mount?
They are all different. |
Agno3
Tinkerer
Username: Agno3
Post Number: 11
Registered: 07-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, December 01, 2009 - 02:24 pm: |
|
This lens is the M42 screw mount. |
Mikel
Tinkerer
Username: Mikel
Post Number: 181
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, December 02, 2009 - 10:39 am: |
|
To disassemble from the front you will need to unscrew the name ring only. Hopefully the filter ring isn't dented and it will come out using a piece of rubber. Once out, you will see how to get the front lens assembly out.
The rear is disassembled by first removing the three set screws in the rearmost ring (black)and taking it off. |
Agno3
Tinkerer
Username: Agno3
Post Number: 12
Registered: 07-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, December 03, 2009 - 10:37 am: |
|
After removing the three screws, I found that the rearmost ring will not come free. The A/M switch extends through the ring and I do not see how to free it.
I was able to get it free enough to see that someone pumped this area full of grease and that is what is causing the issue with this lens. |
Mndean
Tinkerer
Username: Mndean
Post Number: 173
Registered: 08-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, December 04, 2009 - 08:27 am: |
|
I had exactly the same issue (some fool put a ton of grease in the helical because I suspect the lens had been dropped) when I got a Minolta Celtic 135/2.8(early) lens, and really there wasn't much I could do about it. Nobody had taken apart that particular lens that I could find, so I couldn't get any guidance to remove one stubborn lens element next to the aperture (it was the 5/4 design MC Celtic). I gave up on it and bought another lens. |
Tylerwebb
Tinkerer
Username: Tylerwebb
Post Number: 23
Registered: 07-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, August 14, 2010 - 06:40 pm: |
|
I just disassembled this lens. I just tilted the aperture ring up, on opposite side from the A/M switch so you get the most play out of it that way, and then took off the infinity stop bracket. Then I just unscrewed the helicoid past infinity. I know it is a long time since the last post, but maybe you will see this. I will send a PM to the mod too. |
Agno3
Tinkerer
Username: Agno3
Post Number: 28
Registered: 07-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, August 16, 2010 - 10:48 am: |
|
Thanks, Tylerwebb, I'll give it another go. It didn't seem intuitive to do it the way you did.
I appreciate the persistence. |
Tylerwebb
Tinkerer
Username: Tylerwebb
Post Number: 27
Registered: 07-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, August 16, 2010 - 02:55 pm: |
|
I got this lens in a lot of 4 from ebay, including a vivitar zoom, a viv 135 2.8, viv 28 2.5 (which was the real reason I got the lot)
I was very happy when they arrived, although each one had its own problem. None insurmountable though.
The Mamiya had a stuck helicoid. After dis-assembly as described, I cleaned away all the old grease and replaced it with synthetic bike grease. It would have been very easy to also clean the diaphragm return, but mine is very springy and I just rinsed it with a few drops of lighter fluid to be sure. I also put a drop of gun oil on the main spring part.
There is a small ball, however, which would be lost easily if you don't catch it when you take the aperture control ring off.
I also removed the bronze part which twists the helicoid (the part with a large thread for the helicoid and a small thread where it connects to the back end of the main barrel) and re-greased this. This proved the most trouble in reassembly. Everything else was very straigh-forward, but it took me about an hour to get this put back together the right way.
If it is too deeply threaded onto the main barrel side (smaller thread) then minimum focus becomes impossible as something gets jammed.
If it is too shallowly threaded, then there is a gap between the focus ring and the DOF indicator ring which would let all kinds of dirt and other things in.
And then, after finding the happy medium, there seems to be only a small range which is calibrate-able after re-assembly. This is the part that took the most time.
I wish I could tell you exactly how I aligned everything for reassembly, but I cannot be very specific. If I remember right, I twisted the small-threaded side all the way until it stopped, and then untwisted about 1-1/2 full turns to give plenty of space for focusing. Then I carefully threaded the helicoid side until it reached minimum focus and stopped. I then replaced the infinity-stop (which also, obviously works as a minimum-stop) in this position. There are several holes for the bracket screws, and the bracket has wide mounting holes, so it should be possible to mount the bracket anywhere within about a 90 degree range. Getting the minimum stop to fall within this range, however, was the hardest part. I finally got it by getting in the ballpark with about 1-1/2 turns on the small-thread side of the bronze helicoid adjuster part. Then I just threaded the helicoid until minimum focus was reached. I then noted how far away I was from the bracket, IE 30 degrees clockwise. After discovering and using this method it only took a few attempts to get everything aligned properly.
This lens now works awesome! Focus is very smooth, all functions work perfectly. Glass is very clean. I also removed the front element to clean a tiny tiny tiny dot of what I assume was fungus. Mostly preemptive strike. No etching or scratches or discoloration, really perfect glass.
I have been shooting a few portraits with it (mostly of my dogs, my most willing subjects!) and the DOF and Bokeh are awesome. A little bit soft at 1.4, with a bit of flare, but it is a very soft pleasant flare which I don't mind. And at 2 or 2.8 its very sharp, phenomenal quality.
Not too bad for $9 and an hour of tinkering. |
